BAND STRUCTURES, OPTICAL-TRANSITION STRENGTHS AND THEIR PRESSURE-DEPENDENCE OF (GAP)(N)(ALP)(N) SHORT-PERIOD SUPERLATTICES WITH N=3 TO N=10

The electronic structure and optical transition strengths of (GaP)(n)( AIP)(n) short-period superlattices with the clean (001) interface (SL( n,n)) are calculated for n=3 to 10 using the first principle pseudopot ential method within the local density approximation (LDA). The calcul ated results show that SL(n,n) are pseudo-direct gap semiconductors fo r n=3 to 10. The calculated optical transition strengths for the pseud o-direct gap transitions oscillate between even and odd n-values and t hose for even n-values are as strong as those of direct-gap-semiconduc tors, though the transition strengths decrease gradually with increasi ng n. In order to investigate the character of the pseudo-direct gap, the hydrostatic pressure dependence of the pseudo-direct band-gap ener gy and of the optical transition strength for SL(4,4) is also calculat ed. The result predicts that the band-gap becomes smaller, i.e. the ab sorption edge ex hibits a red shift, and the optical transition streng th decrease gradually by applying pressure and thus that the conductio n band state at the fundamental absorption edge is the X(z) state fold ed into Gamma. Copyright (C) 1996 Published by Elsevier Science Ltd